The present invention relates to an improved bridge structure for keyboards and particularly to a bridge structure for reducing sideward inclination angle and shaking.
A conventional bridge structure (as shown in FIGS. 1A through 1D) used in notebook computers generally consist of a first linkage element 1 and a second linkage element 2 which have respectively a leg section 11, 21. The leg sections 11, 21 have respectively a symmetrical first axle 12, 22 located on two sides thereof to pivotally engage with a latch section on a base, and connect two symmetrical arms 14, 24. There is an opening 15, 25 formed between each pair of arms 14, 24. On each of the arms 14, 24, there is a pivotal connecting section 16, 26. The pivotal connecting section 16, 26 have respectively a pivotal tough 17, 27 and a pivotal axle 18, 28. The arms 14, 24 further have respectively a symmetrical second axle 10, 20 which are pivotally engaged with a latch section of a key cap.
When the first and second linkage element 1, 2 are leveled, the pivotal connecting sections are completely matched and coupled. However, when the key cap is lifted by an elastic element, the position of the fulcrum also is raised along the changes of the angle. The movements incur a greater tolerance among the moving elements. When the key cap is depressed, there is no strong supporting point to transfer sideward pressure resulting from downward pressure the key cap received. Hence the key cap tends to tilt and shake at a greater angle when being pressed downwards. It could even cause the first and second linkage element to separate on the engaging location, or result in shaking or loosening off of the key cap.
The primary object of the invention is to resolve aforesaid disadvantages. The invention provides an improved bridge structure to reduce sideward inclination angle and shaking during operations.
To achieve the foregoing object, the invention includes a first and a second linkage element which have respectively two arms each has a pivotal connecting section. The pivotal connection section includes a pivotal trough and an axle. The pivotal trough has a first slant surface section on the bottom section thereof, and the axle has a second slant surface section on the bottom section thereof. The first and second slant surface sections intersect on a juncture to form a fulcrum. When the key cap is lifted by an elastic element, the fulcrum functions as a stationary center point and also as the center of a circle to allow related elements moving about the fulcrum at various angles. Moving tolerances can be maintained without enlarging. When the key cap is depressed, the stationary center point can transfer sideward forces resulting from the downward pressure received on the key cap. Hence sideward inclination angle and shaking can be effectively reduced.